Siri not answering when activated by voice on iPhone 18 Pro

No issues for me on my iPhone 18 Pro or 18 Pro Max, so see if anything here helps you --> If Siri isn't working on your iPhone or iPad - Apple Support

ShilohSophia wrote:

New Iphone 18pro iOS 27.1, Siri will respond to my voice but will not answer, it will answer if I use the side button?

Go to Settings>Siri>Requests and make sure that you don't have "Off" ticked.